1. Field of the Invention
The invention relates to a process for demodulation of a receiving signal that contains, besides the data to be transmitted, a preset synchronization sequence. The invention relates further to an arrangement for performing the process.
2. Description of the Background Art
In modern data transmission processes, a sequence, known in advance, with largely ideal correlation properties is often used as preamble. This makes it possible to have frame and bit synchronization, an estimate of the channel coefficients and possibly the training of an equalizer.
In practice, because of component tolerances, a frequency shift between the local oscillators in sender and receiver repeatedly occurs. If this frequency shift is not taken into account during demodulation, a noticeable degradation in the performance of data detection must be dealt with. Thus various processes for estimating frequency shift have already been proposed. Known, for example, is the use of a nonlinearity for MSK signals (U. Lambrette and H. Meyr, "Two timing recovery algorithm for MSK," IEEE 1994 p 1155/9), the use of an exponentiation process in PSK signals (S. N. Crozier, "Theoretical and simulated performance for a novel frequency estimation technique," Communication Research Center Ottawa, pp 423-428) or the use of an optimal synchronization sequence that transmits the carrier signal with the help of a sequence of constant data (Oliver C. Mauss, Stefan Feuchtinger, "Low complexity digital down conversion and frequency correction scheme for burst mode digital radio," IEEE 1993, p 621-625).